1. Field of the Invention
The present invention relates to a barcode reading mechanism and method for reading, for example, a barcode on a barcode label attached to an item.
2. Description of the Related Art
For example, Japanese Patent Laid-Open No. 2003-288541 discloses a barcode reader having a barcode reading unit which reads a barcode on a barcode label attached to an item by applying a scanning beam of irradiation light to the barcode.
In general, in a barcode reading unit of this kind, there is a need to tilt the optical axis of irradiation light applied to a barcode at a predetermined angle from a direction perpendicular to the barcode label attachment surface in order to prevent a read error due to diffused reflection on the barcode. Barcode labels are standardized in sizes in the length direction of bars constituting the barcode and in the direction of arrangement of the barcode bars.
The position of the optical axis of irradiation light from a barcode reading unit in the barcode bar length direction and the tilting angle of the optical axis vary due to causes in the manufacturing process. For example, if the tilting angle of the optical axis of irradiation light is larger than a set value, the position at which a barcode label is irradiated with irradiation light is shifted in the bar length direction as the distance between the attachment surface of the barcode label and the position of the light emitting portion from which irradiation light is applied to the barcode label is increased. In such a situation, there is a possibility of the bar code reading unit applying irradiation light to such a position that deviates from the attachment surface of the barcode label to cause a read error. In conventional barcode reading units, therefore, it is necessary to adjust the tilting angle of the optical axis of irradiation light with respect to a barcode label.
In a case where the tilting angle of the optical axis of irradiation light from a barcode reading unit is adjusted, the barcode reading unit is set in an adjustment mechanism capable of adjusting the optical axis of irradiation light, and the position of the optical axis of irradiation light in the length direction of barcode bars and the tilting angle of the optical axis of irradiation light are measured. The thickness of an adjusting plate for adjusting the tilting angle of the optical axis of irradiation light is computed on the basis of the results of this measurement. The tilting angle of the optical axis of irradiation light from each individual barcode reading unit is adjusted by attaching an adjusting plate of the desired thickness to the barcode reading unit. In this way, the position of irradiation light in the bar length direction on a barcode label is adjusted.
As described above, the position at which a barcode is irradiated with irradiation light from each barcode reading unit is adjusted by measuring the tilting angle of the optical axis of irradiation light and by using an adjusting plate whose thickness is suitable for adjustment of the tilting angle. Adjustment in such a way requires cumbersome operations and a comparatively long adjustment time.
Moreover, individual barcode reading units vary one from another in the position of the optical axis of irradiation light in the barcode bar length direction, and in the tilting angle of the optical axis of irradiation light. Therefore there is a need to prepare a plurality of kinds of adjusting plates of different thicknesses and to perform adjusting operations using the adjusting plates, and the adjustment operations are cumbersome.